"Senate must fulfill #KimmelTest. Cover for pre-existing conditions, adequate coverage. But in a fiscally conservative way that lowers cost," the GOP senator tweeted Saturday.

Senate must fulfill #KimmelTest. Cover for pre-existing conditions, adequate coverage. But in a fiscally conservative way that lowers cost.— Bill Cassidy (@BillCassidy) May 6, 2017

Cassidy coined the phrase during an interview Friday night, referring to the emotional monologue given by comedian Jimmy Kimmel on Monday about the birth of his son. Kimmel's son was born with a heart disease that nearly cost him his life, but surgery days after his birth saved his life.

During the monologue, Kimmel said he's lucky to have the money to afford insurance and didn't have to worry about whether he could afford to save his newborn son's life. He pointed to the American Health Care Act, a bill passed by the House GOP this week, as something that would harm his son in the future because it allows states to opt out of coverage for pre-existing illnesses.

Cassidy has helped write a bill that would repeal and replace the Affordable Care Act, and is expected to be a major player in the Senate's discussions over healthcare reform.

While the House passed a bill this week, it's expected that the Senate will rewrite the bill during their own discussions and have to work out the differences in conference committee.